`prism-audio-mixer`

The backend logic for the Prism audio control panel (built with QuickShell). This script acts as a bridge between the system's PulseAudio server and the UI. It handles two primary functions: continuously broadcasting the system audio state (volumes, active apps, available devices) in JSON format and executing commands to modify that state.

How it works

State Aggregation (get_state):
- Queries pactl to find the default sink (speaker/headphones).
- Parses the master volume and mute status.
- Iterates through all available Sinks (output devices) and Sink Inputs (applications playing audio).
- Assigns icons to applications based on their name (e.g., Spotify gets a specific icon, browsers get another).
- Outputs a single JSON object containing all this data.
Event Loop (listen mode):
- Subscribes to PulseAudio events using pactl subscribe.
- To prevent high CPU usage from rapid-fire events (e.g., sliding a volume bar), it uses a "trigger file" approach. Events write to /tmp/prism_audio_trigger.
- A separate loop checks this file every 0.1 seconds. If the file is not empty, it clears the file and pushes a new JSON state update.
Control Commands: It accepts specific arguments to change volumes, mute status, or switch output devices.

Dependencies

pulseaudio: Provides pactl for querying and controlling the audio server.
jq: formats the raw audio data into clean JSON for the UI.
gnugrep, coreutils, procps: Standard text processing and process management tools.

Usage

This script is primarily called by the QuickShell UI widgets, not manually by the user.

prism-audio-mixer <command> [args...]

Commands

Command	Arguments	Description
`listen`	None	Starts the event loop, printing JSON state updates to stdout.
`set-volume`	`<id> <vol>`	Sets the volume of a specific application (sink-input ID) to `<vol>%`.
`set-master`	`<vol>`	Sets the default sink's volume to `<vol>%`.
`toggle-mute`	None	Toggles the mute state of the default sink.
`set-default`	`<sink_name>`	Sets the default output device and moves all currently playing audio to it.

JSON Output Structure (Listen Mode)

When running in listen mode, the script outputs a JSON object with the following schema:

{
  "master": { "vol": 75, "muted": false },
  "sinks": [
    { "id": 0, "name": "...", "desc": "Headphones", "vol": 75, "is_default": true }
  ],
  "apps": [
    { "id": 12, "name": "Spotify", "vol": 100, "icon": "" }
  ]
}

Integration Notes

UI Toggle: The 03 QuickShell mixer panel associated with this script is toggled by touching the file /tmp/prism-drawer-volume.
Performance: The 0.1s debounce in the listener loop ensures the UI remains responsive without spamming the audio server with queries during volume slides.